The present invention relates to a temperature-compensating clock pulse generating circuit which generates temperature compensating clock pulses having a deviation of period within several tenth ppm. in a wide temperature range between, for instance, -50.degree. C. and 100.degree. C.
The temperature compensating circuit is effective especially for a timepiece. Recently, an accuracy of a timepiece has been improved since a quartz crystal has been brought into use for a resonator, and the allowable range of error to prove the accuracy of the timepiece has been expressed as a monthly error and further it has been shifted to be expressed as an annual error. However, the timepiece which displays the time accurately to this extent has not been realized by a single quartz crystal resonator which is generally used at present. Accordingly, a wrist watch which displays time accurately by employing two resonators has been put into a practical use by the following two methods. (These methods are illustrated in detail in 9-18 issues, 1978 and 2-19 issues, 1979 of the "Nikkei Electronics") One method is to use two quartz crystal resonators A and B (referred to resonator hereafter) having negative secondary temperature coefficients. The secondary temperature coefficients of the resonators A and B are the same, the peak temperature of the resonator A is higher than B, and frequency at the peak temperature of A is lower than B. The characteristics of the two resonators A and B are set in order that the temperature characteristic of the resonator B at the high temperature side coincides with the peak frequency of the resonator B at the peak temperature of A. And beats of the resonators A and B having the characteristics correlated as illustrated above are extracted to produce various temperature compensating pulses in an electronic circuit on the basis of the beats, and a constant period pulse against time is extracted by inserting the compensating pulse.
The other method is the conventional method in which two X-cut resonators having the same temperature characteristics and different peak temperatures are connected in parallel to act as one quartz crystal resonator equivalently.
Both the two methods have the disadvantages in common. Namely, it is difficult to set the characteristics of the resonators act as one couple, i.e., it is necessary to further select a couple of resonators of within a certain tolerance. Therefore, the resonators, which in the nature of things, could have been housed in one case, cannot but housed separately. Moreover, the temperature range to be compensated, using a couple of resonators, is no more than around between 0.degree. and 50.degree., and this temperature compensating range is insufficient to assure the accuracy of the timepiece to the extent of the annual error of the time display under any areas and any circumstances.